The survey of removal of suspended solids from river at flooding period by plain sedimentation process

The most important of surface sources of water in the large city are rivers. The turbidity and flow rate of rivers is a constantly changing phenomenon in the seasons from year. During rainy period, the run off carries with it silt, clay and sand which make a severe increasing in turbidity to over 1000NTU. The increasing of turbidity causes which the water plant treatment receives the more solides.However; in order to protection of plant units must apply pretreatment processes. In this research, the effectiveness of settling process in order to removal of TSS from raw water was studied. The beginning of the work, lab-scale pilot designed which consisted of a raw water preparation container; the settling column was made of Plexiglas with 2m height, 20cm diameter and the six of sampling ports. The settling column filled with the raw water associated with sediments of river. At defined time steps (30-60-90-120-150-180 min) samples were taken out from the bottom of the column (180cm under water surface). The temperature of water was in the range of 15 to 18oC during experiments. The results showed that between the increasing of TSS removal and settling time, a direct and significant relative (p<0/01) was obtained by Pearson, s correlation coefficient. Also with increasing the depth, the removal efficiency of TSS and turbidity decreased. In the settling time of 30min, 2640mg/L of TSS concentration, the depths of 30 and 180cm, systematically, the TSS removal 92.42% and 80.47% was obtained. when the initial TSS concentration increase to 27640mg/L (the most concentration of TSS), with increasing SOR from 25m/d to 60m/d, the total removal efficiency decreased from 99.2% to 92.2%, and with the TSS of concentration equals to 2640mg/L, the rate of total removal efficiency decreased from 97.2% to 95.7%. The results showed that the rising of SOR and TSS concentration, decreased the total removal efficiency. Also, these are an opposite and significant relative (p